The present invention relates to a seat apparatus for a automobile provided with a head rest, and more particularly, relates to a seat apparatus for a automobile provided with a structure reducing risk of exposing a passenger to whiplash injury at the time of a rear-end collision or the like.
In order to prevent the passenger from being exposed to whiplash injury when a rear-end collision occurs in an automobile or the like, a head rest is provided at an upper side of a seat cushion. An impact at a time of the rear-end collision generates a forward acceleration of the entirety of the seat and a rearward inertia of the passenger, whereby the seat back tilts to a rear side and the upper body of the passenger floats up to an obliquely upper and rear side. Accordingly, when the head rest is provided in a fixed manner, the head portion of the passenger shifts to an upper side of the head rest, so that a large load is applied to the cervical part of the neck and it is difficult to reliably prevent the whiplash injury.
In order to solve the problem mentioned above, a structure in which the head rest is actively tilted forward at a time of the rear-end collision is disclosed, for example, in Japanese Unexamined Patent Publication No. 2000-118280 or the like. The seat for the automobile described in the publication is constructed such that the head rest is supported by a head rest supporting frame which is mounted to a seat back frame so as to freely move in forward and rearward directions, and a pressure receiving member receiving a pressing force of a back of the passenger is fixed to a lower portion of the head rest supporting frame. Furthermore, when a load of the passenger is applied to the seat back at a time of the rear-end collision, the pressure receiving member receives the load, the head rest supporting frame rotates to a front side, and the head rest is tilted forward following thereto, whereby it is possible to support the head portion of the passenger from a rear side so as to securely prevent whiplash injury.
However, when a physical condition of the passenger, a driving condition of the automobile, or the like, does not conform to the structure mentioned above, for example, when the weight of the passenger is low or the automobile speed is low, there have been cases in which sufficient effect could not be achieved due to insufficient forward tilting amount of the head rest. Furthermore, since the structure is made such that the pressure receiving member is arranged between a pair of right and left lower frame plates constituting the seat back frame, the rate of the passenger load applied to the lower frame plates is increased in the case in which the distance between the lower frame plates is small or the lower frame plates are arranged close to the back of the passenger, so that a sufficient load is not transmitted to the pressure receiving member. As a result, there are cases in which the forward tiling amount of the head rest is insufficient and a sufficient effect could not be achieved. Furthermore, in the structure in which the pressure receiving member is provided, the weight and the size of the structure disadvantageously increase.
Accordingly, an object of the present invention is to provide a seat apparatus for a automobile which can reliably and sufficiently achieve an effect of reducing whiplash injury without regard to the physical condition of a passenger, the traveling condition of the automobile, the structure of the seat back frame or the like, and can be provided as a compact apparatus.
In order to achieve the object mentioned above, in accordance with the present invention, there is provided a seat apparatus comprising: a seat back provided with a seat back frame; a head rest frame supported at the seat back frame via a tilting shaft so as to be freely tilted in forward and rearward directions; a head rest supported to an upper side of the tilting shaft in the head rest frame; a gas actuator mounted at the seat back frame, operated due to a momentary gas generation and tilting the head rest frame in a direction in which the head rest is tilted forward at a time of the operation; and an acceleration sensor detecting an acceleration of the automobile in the forward and rearward directions, wherein the gas actuator is operated when the acceleration sensor detects a predetermined acceleration or more.
In accordance with the present invention, when a forward acceleration shock is detected by the acceleration sensor due to a rear-end collision of a automobile or the like, the gas actuator is operated, and the head rest is tilted forward together with the head rest frame. A head portion of the passenger is supported by the forward tilting head rest, and a reduction of whiplash injury is anticipated. Since the forward tilting of the head rest is executed not by receiving the load of the passenger but by detecting the acceleration, it is possible to reliably and sufficiently tilt the head rest forward without regard to the physical condition of the passenger, the driving condition of the automobile, or the structure of the seat back frame. As a result, it is possible to effectively reduce the whiplash injury. Furthermore, since a compact gas actuator can be sufficiently used, it is possible to make the apparatus compact as desired.
In accordance with a preferable aspect of the present invention, there is provided a holding device for maintaining an operating state of the gas actuator so as to maintain the forward tilting state of the head rest. Since the forward tilting state of the head rest is maintained even after the gas actuator is operated, by employing this aspect, the state in which the head rest supports the head portion of the passenger so as to prevent the whiplash injury can be continuously maintained.
Furthermore, in accordance with a preferable aspect of the present invention, a buffering mechanism which allows the head rest frame to tilt forward when the load of forward tilting the head rest frame via the head rest is input to the head rest frame, and prevents the gas actuator from being operated is provided between the head rest frame and the gas actuator. In accordance with this aspect, even when the forward tilting load is input to the head rest for some reason, the load is buffered by the buffering mechanism and is not transmitted to the gas actuator. That is, a reverse operation in which the gas actuator enters into an operating state by the head rest tilting forward does not occur, whereby malfunction of the gas actuator is prevented. In the case of this aspect, it is more preferable that an urging member for urging the head rest frame to a normal position be provided.